Carburizing box



March 17, 1936. H. H. HARRIS 2,034,182

CARBURI Z ING BOX Filed Aug. 9, 1934 INVENTOR HENRY H. HARP/S ATTORNEYS Patented Mar. 17, 1936 UNITED STATES PATENT OFFICE Application August 9,

9 Claims.

This invention relates to carburizing boxes;

It is an object of my invention to provide a carburizing box which will stand up better and longer under the severe usage which such boxes rece1ve.

It is a further object of my invention to provide a carburizing box which will have a longer service life in proportion to the difliculty and expense of making same.

Other objects will appear in the course of this specification.

When carburizing boxes are to be used in heat treating furnaces, metal articles to be carburized are placed in the boxes, together with a carburi5 izing agent such as bone dust. Trays are placed over the boxes, the boxes with their trays are then usually inverted, and in this position subjected to heat supplied from beneath in a heat treating furnace.

The boxes must stand up under rough handling, extremly high temperatures, sudden changes in temperature, and the pressure of a heavy load of contents while softened by heat, all with attendant warping and buckling, producing cracks in the course of time, and ultimately breaking the box down.

As a result, if the boxes were not made so as to have great durability under such treatment, they would have to be replaced constantly at great expense, and it becomes a problem of some nicety and importance to devise a box having the longest life in proportion to the cost of producing same.

I have found that the ordinary rectilinear box breaks down first along the open edges at about the centers of the longer sides, this being the principal locus of failure, a secondary locus of failure being along the open edges at about the centers of the shorter sides.

Experience has also shown that a built-up box is more capable of withstanding strains than an integrally cast or stamped one-piece box, for it can be made lighter and the different portions tend to accommodate themselves and equalize the strain effects.

To make the box of two portions joined centrally along the longitudinal or the transverse axis would place a joint at a major stress area, and the box would give way there all the sooner due to the presence oi the joint.

In the annexed drawing I have illustrated two forms of carbun'zing box constructed in accordance with my invention in which the advantage of a built-up construction is achieved without the disadvantage of having the joints weaken the 1934, Serial No. 739,137

box,- and which is so designed as to be more easily constructed and capable of lighter construction.

In the drawing,

Fig. 1 is a plan view of one form of box constructed in accordance with my invention;

Fig. 2 is a section thereof on the line 2-2 of Fig. 1; and

Fig. 3 is a bottom perspective view thereof;

Fig. 4 is a plan view of a second form of box constructed in accordance with my invention;

Fig. 5 is a section thereof on the line 5-5 in Fig. 4; and r Fig. 6 is a bottom perspective view thereof.

In Fig. 3 arrows lfla and lb indicate respectively the principal and secondary loci of failure.

The carburizing box of Figs. 1-3 is composed of two halves, A and B, formed separately and united together as by welding, along the joint line II. This joint lies in a single plane which passes through the center of the bottom wall and cuts the longer side walls vertically or substantially vertically close to the corners at opposite ends. Each half as thus made constitutes a substantially three-sided portion whose sides provide an end wall, the principal part of a side wall, and a partial bottom wall for the completed box. A bead or thickened edge is preferably formed all along the edge at the open side as shown at l2.

In Fig. 6 the arrows 20a and 20b indicate respectively the principal and secondary loci of failure.

The carburizing box of Figs. 6-8 is composed of two halves, E and. F, formed separately and united together as by welding, along the joint line 2|. This joint lies in a single plane which passes through the center of the bottom wall and cuts the shorter or end walls vertically or substantially vertically close to the corners at opposite sides. A bead or thickened edge is formed all along the edge at the open side as shown at 22.

In each of these constructions the joint not only avoids the major stress areas, but, by having the joint also avoid the corner bend itself, that somewhat critical point is left free of a joint.

It is to be noted that each half of the box has a side wall about it which is substantially flat in parts (as at l3 and M in Fig. l and 23 and 24 in Fig. 4) and which is more sharply curved or bent in other parts (as at l5 and IS in Fig. 1 and 25 and 26 in Fig. 4) terminating in each case in a flat part at one end and a curved part at the other end.

In each case the joint between the halves unites a flat end of one half with a curved end of 55 the other half and the curved end of the first half with the flat end of the second half.

These boxes are usually formed by casting. When they are simply cast as one piece they are made on a solid core, and every part must be made strong enough to take care of casting strains all over, and hence they must be cast relatively thick. With such a two-piece casting every part is subject to less casting strain, and each of the two pieces is shallower than the onepiece cast box, so that casting strains are even further reduced.

As a result the walls can be made thinner and a thickened edge or head provided to give extra strength about the open edge.

It will be obvious that variations and modifications of my invention may be resorted to, and hence I do not wish my invention to be understood as limited to the specific forms shown here.

I claim:

1. A metallic receptacle for use in heat treating furnaces comprising two substantially threesided portions secured together to form a generally rectilinear box having an open top, the joint line extend ng across the bottom wall through substantially the center thereof and up the lateral walls at the corner regions thereof.

2. A two-part carburizing box in which each part has one end of its side Wall more nearly flat and the other end of its side wall more sharply curved, and a joint securing the flatter portion of each part to the more sharply curved portion of the other part.

3. Device of claim 2 in which the two parts are duplicates.

4. Device of claim 2 in which the parts each provide a partial bottom wall and the joint joins the bottom and side walls and lies in a single plane.

5. In a multi-part metallic receptacle for use in heat treating furnaces, a bottom wall, a side wall surrounding same, said side wall having more nearly flat and more sharply curved portions, and joints between the parts extending from substantially the center of the bottom wall to and up the side walls adjacent the more sharply curved portions thereof.

6. Device of claim 5 in which the points lie in the more nearly flat side wall portions and are closely adjacent the more sharply curved portions.

7. Device of claim 5 in which the box is generally rectilinear and the joint is in a single plane forming a substantial diagonal with respect to the bottom Wall.

8. Device of claim 5 in which the bottom wall is rectangular and the joint is in a single generally diagonal vertical plane which cuts the longer, side walls adjacent opposite corners.

9. Device of claim 5 in which the bottom wall is rectangular and the joint is in a single generally diagonal vertical plane which cuts the shorter, end walls adjacent opposite corners.

HENRY H. HARRIS. 

